The dating of Easter Island

What are the dates of Easter Island?

When were the statues erected?

The dates of Easter Island are currently in flux in that the traditional dates have been challenged, so two different sets of dates must be given.

The dates from the island depend on radiocarbon dating. The first, and now the traditional dates were given in a remarkable book “Easter Island, Earth Island” by the British archaeologist Paul Bahn and the New Zealand botanist John Flenley, first published in 1992. These dates depended mostly on pollen analysis. There are many deep bogs in Easter Island in the craters of the volcanoes and it is possible to take a core through the bog showing the successive layers of the build-up, and analyse the pollen found in the different layers.

When John Flenley did this he was able to show that Easter Island was originally wooded, covered with dense forests. But then the tree pollen declined, and flecks of charcoal appeared in the peat core indicating that the forests had been burnt, presumably by man. And from this the theory arose that the forests had been destroyed by the arrival of the Easter Islanders, and that this led to an ecological disaster.

But one of the advantages of pollen analysis is that the bog itself is formed of vegetable matter, which is basically carbon and can therefore be dated, as some of the carbon would originally been radioactive carbon 14, the gradual decay of which provides the basis for radio carbon dating. Most of the dates therefore are not dates for the erection of the statues but dates for the decline of the tree pollen in the bogs. The dates for the decline of tree pollen, and therefore the first settlement, began around AD 900, or possibly a couple of centuries earlier. The erection of statues was in full swing by AD 1200 and the collapse came around AD 1500.

The Bahn/Flenley book had distinct “green” overtones and caused a sensation. Easter Island became the prototype of a civilisation that destroyed itself by its ecological carelessness. The process continued when the ecologist Jared Diamond in his book “Collapse” dealing with the collapse of civilisations, made Easter Island into a chapter all of its own and one of the highlights of the book.

This whole story has now been challenged in a new book “The Statues that Walked” by Terry Hunt and Carl Lipo. They propose a dramatic lowering of the dates so that the first colonisation comes as late as AD 1200. They argue that the trouble with the radiocarbon dating of peat samples is that you never know whether the peat in fact incorporates older material, decaying vegetable matter that has been floating around for centuries and will therefore give a radiocarbon date that is too old. They have therefore taken a look at all the radiocarbon dates from the whole of the Pacific and have subjected them to a rigourous examination , rejecting all the samples that were insecure, and considering only what they consider to be the reliable ones. What happens when you take a more sceptical look and throw out all the peat samples that may be unreliable?

The new dating began in New Zealand. Surprisingly New Zealand is one of the most remote places in the world and was therefore one of the last places to be settled by the Polynesian diaspora that resulted in the Maoris. Indeed from the sailing point of view, New Zealand is almost as difficult to get to as Easter Island, and was therefore settled at the very end of the waves of settlement in which the Pacific was colonised. And New Zealand archaeologists studying the origins of the Maoris began to come to the conclusion that the traditional dates were all far too early and that the Maoris did not arrive until AD 1200. They then went on to analyse the dates of the first settlements for the whole of the Pacific, concluding that it was largely colonised in three separate waves, and that the third wave, includes both New Zealand and Easter Island and Hawaii, was as late as AD 1200. They published their results in a learned paper in New Zealand, which is available on the internet: click here or here

This is the map of the Pacific from the Wilmshurst et al paper, showing the two waves of the colonisation of the Pacific. Their caption: Fig. 1. Islands of East Polynesia, summarizing the two phases of migration out of West Polynesia (blue shading): first to the Society Islands (and possibly as far as Gambier) between A.D. ∼1025 and 1121 (orange shading), and second to the remote islands between A.D. ∼1200 and 1290 (yellow shading).

The paper builds up a formidable case for the late date for Easter Island, which must fit in with the dates for the other islands. The dates for Easter Island cannot possibly be earlier than the dates of the colonisation of the other islands, Tahiti, Tuamotu and the Society Islands which must have been stepping stones for the settlers of Easter Island.

From this Hunt and Lipo build up a completely new story which largely does away with the ecological disaster. The decline of the tree cover was caused not so much human intervention but by the rats inadvertently introduced by the first colonists, who ate the nuts on which the tree cycle depended. There was no ecological disaster, they argue, but a disastrous decline only in the 18th century after the first contact by the Europeans who brought with them diseases to which the Polynesians had no immunity. And these diseases combined with European rapacity destroyed the statue building culture. They point out that when the first contact was made by Roggeveen in 1722, he reported that the island was ringed by statues, but that these had mostly been overthrown by the time that Captain Cook arrived in 1774. This, they say, was the time of the great disaster, not around 1500.

In the meantime Bahn and Flenley have been fighting back with the new edition of their book, now published in Easter Island itself, with splendid illustrations, in which they restate and refine their original position, suggesting that the earliest partial decline of the tree pollen may occur as early as AD 690 or even AD 100, and that it took many centuries for the decline to spread from the original settlement in the south east to the rest of the island. The statue building they say began in earnest around AD 900, and that the ecological crash came around 1500.

The dating of the Easter Island phenomenon and the problems of the causes and dating of the decline are currently in limbo. In these web pages we are therefore inconsistent; generally we follow the traditional position, while I have read with interest the revisionist version. We live in ‘interesting times’, as the saying goes. We desperately need more reliable radiocarbon dates, particularly for the overthrow of the statues and for the activities on Orongo. We will be amending this account as and when any scholarly consensus begins to emerge.